It is known that solids, particularly fine and ultra-fine solids, can cause a variety of problems if allowed to accumulate in various effluent fluids, for example drilling fluid (or muds), sludges and/or slurries. It is also known that some solids can be controlled and/or removed from fluids, at least to a limited degree, using equipment such as (for drilling fluids and muds for example) shale shakers, desanders, desilters, and centrifuges. This type of equipment is known to do an adequate job of removing solids greater in size than approximately three to seven microns. Below this particle size the effectiveness of such mechanical equipment is greatly reduced.
However, if allowed to continue to accumulate, solids smaller than approximately three to seven microns can provide difficulty in a variety of operations. For example, when such solids are allowed to accumulate in drilling muds rheological control problems, decrease in penetration rate and formation damage can occur. In addition, damage to sensitive machinery such as bits and the like (from failure of adequate lubrication) may result. For removal of such fine and/or ultrafine solids it has been recommended that certain chemicals, specifically polymeric coagulants and flocculants, be mixed with the effluent.
While various methods and apparatus for separating solids from aqueous suspension have been heretofore known and/or utilized (see for example U.S. Pat. Nos. 3,929,633, 2,941,783 and 2,852,091) and while devices and methods have been previously suggested and/or utilized for separating particles from fluids in general (see for example U.S. Pat. Nos. 4,756,823, 4,174,278, 4,431,548, 4,758,332, 4,692,237, 4,539,099 and 4,511,479), such apparatus and methods heretofore known have not provided an integrated system for the makeup of dry polymer, polymer blending, polymer injection and mixing with the effluent, floc forming, and effluent preconditioning and chemical preparation in a relatively compact and portable structure with a centralized control system.
With regard to polymer flocculation, it is known that the long chain polymers utilized for water treatment processes are shear-sensitive, and thus must be introduced into the effluents while avoiding destruction of the shear-sensitive floc formed therewith. However, thorough blending is also required of the polymer material with the effluent in order to achieve adequate floc formation.
It is also known that, when utilizing polymers in dry form as a coagulant, flocculent or the like (for example products produced by Allied Colloids Company such as the trademark products Percols 351, E-24, 155, 156, 721, 728, 753 and 788N), preparation of a concentrated stock solution is desirable to assure proper activation of the polymer in its liquid phase (for example water). It would be desirable therefore, during this polymer dispersion process, for the polymer particles utilized to be prewetted to decrease the dispersion time and prevent the formation of lumps (known as fisheyes) of the polymer material which dissolve very slowly, if at all, due to formation on the outer surface of such lumps of a highly viscous gel which resists passage of liquid necessary for further wetting of the polymer.
While the need in various water purification processes for gentle but complete blending of polymers with effluents and for adequate dispersal of polymers in their aqueous phase is recognized, apparatus for achieving such goals have not always proved effective, and further improvement therein could still be utilized.